Stabilized pulverulent compositions and process of manufacture thereof



Patented May 26, 1953 s PATENT oFFICE STABlLIZED PULVERULENT COMPOSI- TIONS AND PROCESS OF. MANUFAC- TURE THEREOF Edwin W. Tillotson, Pittsburgh, Pa., assignor to Garco Products, Inc., Allegheny County, Pa., a. corporation of Pennsylvania No Drawing. Application July 20, 1950,

Serial No. 175,032

The present'invention relates to stabilized'pul- -verulent compositions containing finely divided glass and to a process of obtaining these compositions.

One object of the invention is to provide means for controlling the alkalinity of a pulverulent mixture, including a substantial proportion of glass, during storage and handling thereof. A secondob'ject of the invention is the provisionof a stabilized finelydivided silica-glass mixture which 'is commercially acceptable the production of vitreous ware. Other objects and advantages of the invention 5 will be apparent from the following detailed de- -*scription of a preferred embodiment thereof 1 Mixtures containing finely divided glass have "achieved adefinite utility in certain industrial applications. For example, some types of cellular glass are formed from such mixtures. Enameling or glazing slips and even the molding matrix include quantities of pulverized glass. Despite the advantages to be gained through the ready availability of glass in these mixtures, there is an accompanying problem of material control. The finely divided glass particles present a large total surface area susceptible of attack by water. Leaching of the alkalies in the glass upon contact with moisture results in the formation of basic compounds, such as sodium hydroxide, and so increases the alkalinity of the mixture. The degree and time of hydrolysis are, of course, almost impossible to predict, and the erratic increase in alkalinity will create operational difiiculties and losses.

Briefly stated, therefore, my invention contemplates the addition of an acidic material to a mixture containing finely divided glass, in order to neutralize alkali formed therein upon exposure to moisture and thereby to maintain a reasonably constant pH in that mixture.

It will of course be readily apparent that all acidic materials will not be applicable to the invention. Since many glass containing compositions are admixed with water during their preparation or use, a readily soluble acid component would be washed out thereby, and its stabilizing effect lost. I have ascertained the metallic salts of fiuosilicic acid to be particularly adapted for stabilization according to the provisions of my invention. These compounds have a low solubility in water and accordingly will not be removed during the ordinary processing operations. The compounds are stable to a degree that they will not induce decomposition within the glass mixtures being protected thereby, yet their acidic nature will insure rapid neutralization of free 6 Claims. (01.106-52) I bases liberated in those mixtures.

Of the many 1 metallic fiuosilicates, I prefer to employ potasslum fiuosilicate because of its ready availability,

reasonable cost, and the nature of its operations in actual use. v I

The invention isnot limited in its application to any particular glass containing mixtures, except insofar as the glass is in finely divided form. I have been interested in the stabilization of waste sand mixtures resulting from the grinding or surfacing of plate glass with sand as an abrasive. This material is so fine thatnearly all of it will pass a screen of 325 mesh and it ordinarily contains from 12 to 25 per cent of glass; Because of its fine state of division it is readily combined with clays, lime and comparable materials, and may be used in the manufacture of various ceramic wares. In this instance the glass will serve as a substitute for a portion of the fiuxing agents normally employed. But, as previously mentioned, the glass is in a form most open to attack by moisture and even with careful control unstabilized'waste -sand mixtures occasion operational difiiculties which preclude its use.

In accordance with my invention, the waste sand-glass mixture is stabilized by adding thereto a small quantity of finely divided alkali metal fiuosilicate and preferably potassium fiuosilicate. For convenience, the addition accompanied by agitation or other suitable mixing may be made to a slurry of the waste sand after the raw material, discharged from the plate glass grinding operation, has been purified and concentrated. The treated slurry is then filtered and dried. The stabilized mixture will have a pH of about 4.0, and this will remain constant indefinitely in the absence of moisture.

The amount of potassium fiuosilicate required to stabilize a Waste sand-glass mixture will depend upon the initial pH of the mixture undergoing treatment. It has been observed that a waste sand slurry, purified and thickened, has a pH of from 10.0 to 10.5. Potassium fiuosilicate in an amount of from 0.75 to 3 per cent by weight or" the dry solids content of the slurry will reduce the pH thereof below 4, and will maintain an acid condition for a prolonged period of time. Larger amounts of potassium fiuosilicate may be incorporated if desired, although such procedure will be uneconomical. Smaller amounts of potassium fluosilicate are permissible where the mixture being stabilized is in substantially dry form and will not be exposed to highly humid conditions.

By way of a specific example, to a waste sand- Days of Storage Although the hydrogen ion concentrationlis nor- .inially cousideredmas.zaameasure ..of-r theacidity or v alkalinity of .a'. solution, for: ,thegDLlrDQseswofL this "invention, therexpression denotes Jthe .raciditysor ialkalinityzofaa suspensionrorrslurrylof solids in water. Dry o1: substantiallywdryisamples of; stabilizedanixtures are dispersedv in water'.tol forma Jslurry "which tng ay .be evaluated 1 S mply and nui k'lr.

'IIt will. be apparent from therioregoingtdeescription that .the;desired. stabilization isJobtai-ned thrdughthe application of ..my inventive-icon cept, .The controlled .alkalinity not the waste "sand-glass mixture permits "(the incorporation thereof A. in "ceramic batches without ndifiiculty. The, previously observed operational a difficulties accompanying the use of un stabilized' mixtures v containing finelyudivided;glass.1are no lon er a problem. Itis clear, therefore lthatqmyinvention has:.madeaaxailablewto: .thesceramicsaindustry a a 4 vast supply of valuable raw material hithertofore regarded as impractical or unusable.

What I claim is:

,1. A process of stabilizing-,8. pulverulent mixture consistmg:essenflalllwoffiflnelylidivided glass and silica which comprises incorporating therewith from 0.75 to 3 per cent by weight of potassium fluosilicate.

L2. Arzprocessrofzstabilizing a pulverulent mixtturelconsist'ingr.essentially of finely divided silica vand glass which comprises incorporating therewithapproximatelyl per cent by weight of potassiumtfiuosilicate.

13. A, process ofsstabilizing a pulverulent mixture vconsisting essentially of finely divided silica andzglass which comprises forming a slurry of the pulverulent mixture containing approximately l50,iper cent by weight of solids, incorporating 1.25 per cent by weight of the solids content 01. the slurry oi finelyi divided potassmmfiuosilioate, lvagitating'the treated slurrymoinsurhomogeneity thereofvandifiltermg the slurry.

4. A pulverulent mixture of contrlldmlln- .wlinity consisting .essentiallynofflfinelydividedtglass t and, silica. andl'froml 0 .75wto 3,.perwcent',byaweight of potassium fiuos'ilicate.

5. A pulverulent mixturevofcontrolled-salmity consisting v essentiallyrof; 'flnelyidividedd silica and ,1 glass 'rhaizing sadmixed r therewith approximately 1- per. centiuby weightbf potassium 1"fluosilicate.

.6. Ah pulverulent mixture of.contrblled,ralkalinity containing-Thom. 74411037,rperacentxbymoight arxmewmvmm. silica, J fmmf. 12 to25, .pe1x:cent

.r fin'elyJdiVideid,glass andiapproximatelytLperxent I by weightoflfinelykiivided,potassiumifluosilinate.

W.-='TILLOTSON.

r'EOREIGM FPATEN'IZB -Number QCOur'xtry l Date 5367,53 "l Germany 1923 

1. A PROCESS OF STABILIZING A PULVERULENT MIXTURE CONSISTING ESSENTIALLY OF FINELY DIVIDED GLASS AND SILICA WHICH COMPRISES INCORPORATING THEREWITH FROM 0.75 TO 3 PER CENT BY WEIGHT OF POTASSIUM FLUOSILICATE. 